In the field of mining, trams are employed to move coal hoppers in and out of mines. The trams available at the present typically employ a transmission which includes a pair of sprocket wheels, the first of which cooperates with a worm gear which is rotated by a motor, and the second is connected to the first with a chain. The second sprocket wheel is also connected to a drive shaft which in turn engages a caterpillar chain which is supported by the mine floor, thus when the motor is on, the worm gear turns the first sprocket wheel which engages the chain and thereby turns the second wheel, the second wheel then turning the drive shaft thus moving the caterpillar chain and hence the tram.
This transmission is inefficient in that a large percentage of the power produced by the motor is lost in the worm gear, thereby requiring a much larger power output to move the tram, with a resulting speed lower than desired for the corresponding power output. Due to this inefficiency the tram may easily bog down when it is driven into mud or the like. In this configuration the relative size of the first and second sprocket wheels determine the speed of the tram in relation to the rotational velocity of the motor. Typically the two sprocket wheels are the same size, thereby rotating the drive shaft at the same speed as the motor. This creates the need for a motor with a lower rotational velocity so that the tram may crawl at the desired speed, this motor being less efficient than a motor producing the same amount of torque but with a faster rotational velocity. The sprockets are connected to shafts which are typically of a relatively small diameter as compared to the sprocket wheels, which inhibits premature breaking of the shafts, due to the transference of torque from a large diameter to a relatively small diameter. In this atmosphere, the chain is easily clogged with coal and other debris and therefore is easily broken. The breakage of the sprocket wheel shafts and the chain cause undue expense for repair and lost operation time.
Therefore, it is an object of this invention to provide a means for moving a tram into and out of a mine shaft while employing a more efficient motor.
It is also an object of this invention to provide a means whereby the torque produced by the motor is transferred to the drive shaft of the tram more efficiently thereby requiring a lower torque output from the motor.
Another object of this invention is to provide a means whereby the rotational velocity of the drive shaft may be reduced in relation to the rotational velocity of the motor such that a motor with a higher rotational velocity may be employed.
Still another object of this invention is to provide a means whereby the components are shielded from debris and moisture.
Yet another object of this invention is to provide a means whereby the gears and bearings may be lubricated, with the lubricant being protected from contamination, thereby increasing the life of the components due to less wear.